Probe for detecting and locating sources of electromagnetic energy



Aprll 26, 1949. M. P. VAN CAMP ET AL 2,468,143

PROBE Fon DETECTING AND LOCATING soURcEs 0E ELECTROMA'GNETIC ENERGY Filed Nov. 3, 1944 Patented Apr. 26, 1949 'PROBE' FOR DETECTINGI ANDLOCATING SOURCES OF ELECTROMAGNETIC EN- ERGY 'Marguerite P. Van Camp,V Detroit, and Joseph L. 'McFarland Royal 0ak,"Mich.

Application November 3, 1944, Serial No. 561,798

6 Claims.

f(Granted under the act of March3,' 1883, as amended `April '30, 1928; 370 O. `G. 757) "The in-vention desoribed'he-rein maybe' manufactured andused'byI or for the Government for vgovernnriental purposes, 'without the payment to "us of 'anyvroyalty thereon.

` This invention relates to probes an-d more par ticularly/to' anielectricalprobe for the location Iand-isolationA :3f-"interference in electrical and radio apparatus.

The objects of the present invention include "the provision of an Iimproved interference locating electrical probefor spottingv zones of radio *frequencyinterferencein and about radio interference generatingv apparatus; ofa probe'hav- 'ing multiedirectional characteristics that makeit unnecessary "to 'rotate lthe probein orderto lov"cate various sources Aof radio frequency interference; of a probe'of'improved sensitivity that is ycon-centr-ated'in asmall, compact and kslender construction that `permits its insertion into small recessesthat have Ybeeriinaccessible to commercial'V probes that Ahaveibeenavailable heretofore; of a probe that-'isrof improved simplicity in construction andin'-"modeof operation, permitting fitsuse Iby nonete'chn-ical personnel, and vthat is simplefofassem'bly so that it'may be manufactured rapidly andi inexpensively with a minimum 'of `apparatus',"operations and expense; of a probe 1 that lis 1 provided withan vinsulating sleeve that `protectsf'it against undue damage, wear and foul- Aing bwmetal-particles, moisture, dirt and the like, `andthat jeliminates the possibilities of shorting piecesv Aofielectricalapparatus which may be con- Ytacted'loyl it and which preventsthe creation of *undue fstatic' discharges should the probe rcon- -itact any"metal'object;y of a probe that is provided I with mechanicaliattentuator that assists in the regulation -of its fradiol `frequency pick-up, and

lof a-probefwh-ichm-ay be easily, denitely set at i a given distance-'from afgivenpoint and positively 1 "maintained: atfthat distance.

'.Withtheaiabove, rand 'other' objects fin' view,

Fig; 1 isfasideuelevation (mostly brokenaway) of the; ,probe `assembly;

Figs zfisa-.sideelevation of the probe 4assembly distancerrgauge applied;

x. Figi-:.4 siazsideiel'evationinf. the probe assembly,

--iiistancefgaugenandmocperatingf housing;

' ofthe probe Awire or Wires. loops, at that point, may cross the axis ofthe barrel I'diametrically from one shieldtubeM end (see Fig. 8).

Fig. 5 is a side elevation of the attenuator;

Fig. 6 is a side elevation of the probe assembly, with attenuator and housing in position;

Fig. '7 is a side and Ybottom plan view of afcoil shield;

Fig. 8 is an end view of the probe; and

Fig. 9 is a front view of coil shield mounting base.

The invention comprises an electricalv probe, a tubular attenuator cooperating therewith, land a distance gauge and housing cooperatively mounted on the probe, the housing being provided with a scale which may cooperate'with the attenuator to determine the desired position of the attenuator.

The probe proper comprises a tubular barrel i of brass or other non-magnetic material,l one end of which is detachably secured by set screws or the like to one end of a transmission `cable"'2,

which includes two inner conductors 2|,22 arid an outer conductive shield 23.

l The operative or sensitive portion of the probe consists of a plurality of wire loops formed'from one or more probe wires 3, and disposed as-sub- `stantially identical elliptical loops approximately parallel with the longitudinal axis of the probe, as more clearly shown in Figs. 1 and 8 ofthe drawings. In 4the varrangement illustrated, "one continuous probe wire 3` is'used. Thebranches of these loops are shielded by enclosing nonmagnetic tubes 4 rmly seated in respectiveibores in a suitable basefplug or disc' 5,` securedinfthe end` of barrel I in any acceptablemanner. The free ends of tubes 4 are curved-inwardly `toward the common centeror probe axis, and tapered by being cut ofi 'at a 45 angle at each side.

"These four tube-ends closely approaching-each `other present, between them, invassembled -relation (as shown -in Fig. 8), an X-shaped passage or pickupslot crossed `by the closed ends of loops As will be seen, these to another andv at right angles to 'each-other. It shouldbe noted that the ends ofthe `tubes 4 are spaced one from the vother,leaving the probe Wire exposed only as a cross at the probe This spaced Y relation of shield tubes 4 is positively maintained by a short, icylindrical 'spacer 6 of insulating materaLlongitu- 4dinally drilled for passage lof the`tubes-4 therethrough. It will be well understood thatvarious 'other loop arrangements'than'that showntmay be used, and alsothat afV greater number-"o-pobe wiresmmay Sbe used, The.V endsf'of 'itheapr'obe wire or wires are carried back through the barrel I and are secured in any usual and well-known manner to the conductors of the transmission cable 2.

This construction provides narrow, elongated, intersecting, pencil-like, probe-wire loops in an exceptionally compact arrangement capable of ready insertion within very restricted spaces or openings wherein existing probes are incapable of use.

It is hardly necessary to state that the opposite end of the cable is connected in well-known manner to any acceptable indicating equipment.

Near each end of the barrel I, circumferential grooves I'I are formed therein to seat resilient spring washers or split rings I8, which extend radially appreciably beyond barrel I to frictionally engage and support a protecting housing Q. Housing 9 is of insulating material such as a plastic of any one oi several acceptable types. It is a cylinder of ample overall length to completely enclose the entire probe, and is closed at one end. Its opposite end may be longitudinally split to provide clamping jaws operable by the ring clamp I2. When in place, this housing El completely protects all parts of the probe against all objectionable metallic and electrical contacts, and amply protects it against possible short circuit, and against the entrance of moisture, metal particles, and other foreign matter.

It is desired to use the probe at known distances from a source of interference. Accordingly a calibrated sleeve B of any acceptable insulating material is provided. This sleeve, when in operative position, extends the full length of and encircles the probe (Fig. 2). It is secured in place upon the barrel I by a set screw or the like (not shown), after rst removing both of the split rings I8. Sleeve 3, when assembled on barrel I', does not extend radially a greater distance than do split rings I8 when in place. Cooperating with this calibrated sleeve is the housing 9 of sufficient diameter to nt slidably over sleeve 8. It is provided, about midway of its length, with a longitudinal slot III having a calibrated edge or edges II, for a purpose to be later disclosed. Preferably, the open end of housing 9 is longitudinally split to provide compressible jaws, in well-known manner. An ordinary ring clamp I2, with i'lnger lever I3, suitably mounted on the split end, is used for clamping the housing at various positions of adjustment along the sleeve 8. In using the distance gauge, the probe is slidably adjusted within the housing 9, as desired. The distance of the sensitive end of the probe from the noise source is indicated by the reading of the exposed portion of the scale on the sleeve 8, the end of the housing 9 acting as a scale index or pointer, as shown in Fig. 4. The clamp I2 is then tightened to securely hold the probe in this position with its sensitive end spaced such distance from the inner end of housing 9 (see Fig. 4). By placing the closed end of housing 9 against the object from which the interfering noise emanates, the probe may be denitely held at that exact known distance from the source of noise. This may be repeated, denitely increasing or decreasing the distance as may be desired.

In many instances an attenuator will be desired. It serves to adjust or regulate the amount of radio frequency energy that may be picked up by the sensitive portion of the probe, and to correspondingly localize the same.

The attenuator comprises a cylindrical attenuator tube Il of brass or substantially equivalent non-magnetic material, of such inside diameter as to travel ireely over barrel I after removal of the split ring I3 proximate to the sensitive end oi the probe, and is used directly on the probe without sleeve 8 or after removal of sleeve 8 (see Figs. 3 and 5). Preferably, its inside diameter is such as to make a snug sliding fit about barrel l and it is of such thickness as to permit free movement within housing 9. One end may be longitudinally split to provide yielding spring action in assembling and in operation. It should be long enough to cover the full length of the sensitive part of the probe and still overlap the adjacent end of the tube I of the probe body. To secure the attenuator at various adjusted positions, a set screw I5 is provided. This screw is threaded through the side wall of the attenuator tube M and, in operation, binds against the barrel i, locking the two together.

In order to indicate the position of the attenuator relative to the sensitive portion of the probe, the scale I i' is provided. Set screw I5 is provided with an extended shank I6, adapted to travel freely in the slot IEB in housing 9. In using the attenuator, the sleeve 8 is removed, one of the split rings I8 is positioned upon the end of barrel I proximate to the cable 2, attenuator tube I4 is slipped over barrel I, housing 9 is slipped over the attenuator tube Id, and along the probe to the full length of the probe where it is clamped, `set screw i5 is passed through slot I0 in housing S and threaded into tube lll sufciently to connect said tube and screw E5, but not far enough to bind the attenuator to the probe. Then the attenuator is moved lengthwise of the probe by the projecting knob end of the set screw I5. The attenuator is secured at any desired position by simply tightening screw I5. The relative position of the attenuator at any particular time is indicated by the position of the set screw I5 relative to the scale I I' (see Fig. 6).

It will be seen that the invention may be used as a probe protected by housing 9; as a probe with the calibrated sleeve 8 and housing; and as a probe with attenuator and housing 9.

It is thought that the construction, operation, and use of the invention will be clear from the preceding detailed description. Changes may be made in the construction, arrangement, and disposition of the several parts of the invention within the scope of the appended claims, and it is meant to include all such within this application wherein only one preferred form of the invention has been disclosed purely by Way of illustration and with no thought or intent to, in any degree, limit the claims thereby.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. A device for coupling a source of stray electromagnetic energy to a utilization circuit comprising, a balanced shielded line, said line including an outer shielding conductor and two inner conductors, one end of said line being connected to said utilization circuit, a coupling member connected to the other end of said line, said coupling member including a tubular barrel of conducting non-magnetic material electrically continuous with said outer shielding conductor, four tubes of conducting non-magnetic material eX- tending longitudinally from one end of said barrel, disposed substantially in quadrature about its axis and electrically continuous with said barrel, the distal ends of said tubes being bent inwardly into opposing spacedrelationship, a continuous wire, insulated from said tubes and barrel, having its opposite ends electrically connected respectively to said inner conductors eX- tending through said four tubes so as to form two serially connected loops whose planes are subu stantially perpendicular to each other so that said loops are substantially completely shielded by said tubes and the balance of said Wire is shielded by said barrel.

2. A device as dened in claim 1 which includes an attenuator, said attenuator including a tubular member of conducting non-magnetic material encircling said barrel and electrically continuous therewith and slidable longitudinally thereon, so that said attenuator may be moved so as to have the outer end overlap, by varying distances, the four tubes and the loops of wire extending therethrough, so to vary the degree of coupling between said coupling member and said source.

3. A device as defined in claim 1 including a cylindrical housing closed at its outer end, of dielectric material, enclosing said coupling member.

4. A device as dened in claim 1 which includes an attenuator, said attenuator including a tubular member of conducting non-magnetic material encircling said barrel and electrically continuous therewith and slidable longitudinally thereon, so that said attenuator may be moved so as to have the outer end overlap, by varying distances, the four tubes and the loops of wire eX- tending therethrough, so to vary the degree of coupling between said coupling member and said source, and a cylindrical housing closed at its outer end, of dielectric material, enclosing said coupling member and said attenuator and secured to said coupling member so as to allow full operation of said attenuator.

5. A device as defined in claim 1 above including a sleeve of dielectric material encircling said coupling member, a cylindrical housing, closed at its outer end, of dielectric material, encircling said coupling member and said sleeve and longitudinally slidable upon said sleeve, and a scale to indicate the longitudinal position of the housing relative to the coupling member.

6. A device for coupling a source of stray electromagnetic energy to a utilization circuit comprising, a balanced shielded line, said line including an outer shielding conductor and two inner conductors, one end of said line being connected to said utilization circuit, a coupling member connected to the other end of said line, said coupling member including a tubular barrel of conducting non-magnetic material electrically continuous with said outer shielding conductor, a plurality of pairs of tubes of conducting non-magnetic material extending longitudinally from one end of said barrel and electrically continuous with said barrel, the distal ends of the tubes of each pair being bent inwardly into opposing spaced relationship, a continuous wire, insulated from said tubes and barrel, having its opposite ends electrically connected respectively to said inner conductors and extending through said tubes so as to form a plurality of serially connected loops whose planes are angularly disposed with respect to each other so that said loops are substantially completely shielded by said tubes and the balance oi said wire is shielded by said barrel.

MARGUERITE P. VAN CAMP. JOSEPH L. MCFARLAND.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATESV PATENTS I OTHER REFERENCES Short Wave and Television, April 1938, pages 669, 706, 707. 

